Immature and mature nonstratified seeds of white ash (Fraxinus americana L.) were dissected transversely and 2/3 of each seed was placed onto agar-solidified Murashige and Skoog medium. Adventitious buds, shoots, and somatic embryos formed on callus, cotyledons, and hypocotyls of the resulting seedlings. Shoot organogenesis was induced on explants cultured on medium with 10 μM thidiazuron but not on explants on media with benzyladenine (BA) or isopentenyladenine. Not all seed sources were equally capable of shoot organogenesis and embryogenesis. Atypical of adventitious regeneration of other woody plants, mature seed explants of white ash were more organogenic with shoots that elongated better than explants from immature seeds. Somatic embryogenesis was observed in cultures where mature seeds were first cultured for 4 weeks on a medium containing 10 μM adenine 2,4-dichlorophenoxyacetic acid in combination with 0.1 and 1.0 μM thidiazuron, followed by transfer to a medium containing 0.05 μM 6-benzyladenine and 0.5 μM naphthaleneacetic acid. Adventitious shoots and epicotyls from both seedlings and germinated somatic embryos were rooted under intermittent mist and acclimatized to the greenhouse.

Thidiazuron stimulates shoot organogenesis and somatic embryogenesis in white ash (Fraxinus americana L.)

Elderberry: Botany, Horticulture, Potential

We report here the successful micropropagation of adult Juniperus phoenicea L. with respective ploidy stability studies. Microcuttings with axillary buds were grown on five media supplemented with different growth regulator combinations. Best elongation rates were achieved on Driver and Kuniyuki (DKW) medium supplemented with kinetin alone or with naphthaleneacetic acid (NAA), while Rugini olive (OM) medium stimulated the development of new branches. Shoots growing on Murashige and Skoog (MS) medium browned and showed necrotic zones. Shoots of second to fourth subcultures usually had higher elongation rates than those of the first culture. For rooting assays, half strength DKW and OM media, different concentrations of growth regulators, auxin continuous exposure vs. dipping and the type of solid matrix were assessed. During rooting assays, two morphotypes were observed with one type having well developed internodes and the other showing hyperhydratation and no internode development. High rooting rates (40 %) were only obtained in the first morphotype shoots exposed for 5 min to 2.4 µM IBA and then transferred to OM medium without growth regulators. Plants were acclimatized in pots containing a mixture of peat and Perlite (3:2) in greenhouse with progressive reduction of relative humidity. A flow cytometric screening for major ploidy changes revealed no differences among the morphotypes and between them and the mother plant. Also the nuclear DNA content of this species was estimated for the first time using flow cytometry (2C = 24.71 pg).

Micropropagation of Juniperus phoenicea from adult plant explants and analysis of ploidy stability using flow cytometry

In contrast to previous reports, the endocarps (‘‘seed coats’’) of Sambucus species are not impermeable to water; thus, the seeds do not have physical dormancy. Seeds of the North American species Sambucus canadensisand S. pubens and of the European species S. racemosa have spatulate shaped embryos that are ;60% fully developed (elongated) at seed maturity. The embryo has to extend to the full length of the seed to germinate. Embryos in freshly matured seeds of S. canadensis and in those of S. pubens grew better at 258/158C than at 58C, whereas the rate of embryo growth in S. racemosa was higher at 58C than at 258/158C. Seeds of all three species germinated to significantly higher percentages in light (14-h photoperiod) than in darkness. Fresh seeds of neither species germinated during 2 wk of incubation over a range of thermoperiods. Warm followed by cold stratification broke dormancy in seeds of S. canadensis and in those of S. pubens. Thus, seeds of these two North American species have deep simple morphophysiological dormancy (MPD). In comparison, seeds of the European species S. racemosa required a cold stratification period only for dormancy break, and thus they have intermediate complex MPD. GA3 was much more effective in breaking dormancy in seeds of S. racemosa than it was in those of S. canadensis or S. pubens.

https://bsapubs.onlinelibrary.wiley.com/doi/pdf/10.2307/2656744

Morphophysiological dormancy in seeds of two North American and one Eurasian species of Sambucus (Caprifoliaceae) with underdeveloped spatulate embryos

Actinorhizal plants are a diverse group of trees and shrubs that have the ability to form a dinitrogen-fixing symbiosis with Frankia bacteria. Actinorhizal plants are found throughout the world and are a significant component of rangelands in the western United States. Many actinorhizal species play important ecological roles in the habitats where they occur. Actinorhizal shrubs such as bitterbrush (Purshia tridentata [Pursh DC.]), mountain mahogany (Cercocarpus spp), and Ceanothus spp. are among the most important wildlife browse species in the western U.S. Other actinorhizal taxa such as alders (Alnus) and dryads (Dryas) play important roles in soil development and community succession following disturbance. Despite their importance, the biology of these plants in rangeland ecosystems is poorly understood. Particularly lacking is understanding of the dinitrogen-fixing ability of these plants and how symbioses with Frankia bacteria affects the ecology of these plants in western U.S. rangelands. Difficulty in isolating and culturing Frankia bacteria and in measuring inputs of fixed N from actinorhizal plants has contributed to slow progress in this field. In spite of these shortcomings, the actinorhizal plants of western U.S. rangelands represent a valuable resource for expanded utilization. This review is a summary of current knowledge of actinorhizal range plants and their Frankia symbionts. It is intended to provide a scientific basis for the study and utilization of this symbiosis for those involved in rangeland research and management.

/pdf/actinorhizal-plants-in-rangelands-of-the-western-united-11zl2u8wva.pdf

Actinorhizal plants in rangelands of the western United States

The reference manual of woody plant propagation: from seed to tissue culture: a practical working guide to the propagation of over 1100 species, varieties, and cultivars , The reference manual of woody plant propagation: from seed to tissue culture: a practical working gu... , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Michael A. Dir

Papers

The Reference Manual of Woody Plant Propagation : From Seed to Tissue Culture